'KROT2-XM' (mole), new project Xmega32

[reptooyep]

I first made this RX value coil but few posts ago, timekiller told me that the ratio was too big for ballancing correctly.
That's why i made a 165 turns One and at last 142 turns. He told me that the ratio should be 1/10.

[Koala]

Do you have a oscilloscope.

If so does the wave form of the Rx alter as you shift the position of the Rx to Tx

[reptooyep]

Hi, i hqave a vintage 60Mhz scope from the early seventies...
I can se the phase shifting and the level of the RX decrease but never under 400mv ...
I think i'll put again my 22.5 mh coil and try again.
My Tx is 45t of 0.5mm wire (1.07mh).
I have now 3 RX coils :
142t 11.7mh
165t 14.7mh and
200t 22.5mh (all 0.15mm wire)
Which one would be the best ?

[Koala]

Hi, i hqave a vintage 60Mhz scope from the early seventies...
I can se the phase shifting and the level of the RX decrease but never under 400mv ...
I think i'll put again my 22.5 mh coil and try again.
My Tx is 45t of 0.5mm wire (1.07mh).
I have now 3 RX coils :
142t 11.7mh
165t 14.7mh and
200t 22.5mh (all 0.15mm wire)
Which one would be the best ?

You can bending the coils slightly to fine tune it or try moving a small piece of ferrite between the overlap.

Altering the induction affects the phase not the nulling. I would stick with the original specification at least till its up and running.

[reptooyep]

My coil is in a a shell, so, i can't move it a lot but i can see the "nulling" position whith the minimum signal but still 500mv..
I'll continue my investigations tomorow.

[reptooyep]

I just notice something,
I use USB cable which has only one screen,
Maybe it's the cause of my nulling troubles ?

What kind of cable would fit this detector ?

[Koala]

I use Van Dammed 4 Core Microphone Cable for all my VLF coils. Nice and flexible. Tried a cheap USB2 cable worked fine on the bench. Seemed like it was more sensitive to being knocked.

Get the null correct before attaching the shield. The phase does alter a bit when the shield is added but not enough to worry about

[blobber]

Hi friends,
I want to share my experiences with this great project.
First I want to say a big thanks to Andrew, the autor from the Mole project. Thank you, that you share all information with us!!
Well, I have made two versions, DIP and also SMT, both are working very well with my selfmaded DD27 coils. I read all information here in this thread and also on Andrews web site, there by using google translator.
I tried also most of the different firmwares, for me the best working version is K2-GAIN-SGold, with both DIP and SMT.
But this is only my opinion, in my case I can detect 1 € in air, by 35cm without any false signals and until 45cm with a lot of false signals, depends of the sensitivity adjustment. Of course I used my Mole in soil, by reducing sensitivity and I was able to found the good things...
Fred

[blobber]

Hi Andrew,
I want to ask you about this video here:

*https://m.youtube.com/watch?feature=...&v=QI-RRsqRRvg

Which firmeware you are using here, can you please share with us?
Filter F4 discrimination for bottle caps..

[CDI]

Hi Andrew,
I want to ask you about this video here:

*https://m.youtube.com/watch?feature=...&v=QI-RRsqRRvg

Which firmeware you are using here, can you please share with us?
Filter F4 discrimination for bottle caps..

Hi Blobber, can you please post correct DIP lay version that u maked? Thanks.

[blobber]

my working DIP version.zip

Hi Blobber, can you please post correct DIP lay version that u maked? Thanks.

yes for sure

[blobber]

But I have made some mods, a bit smaller board and using some SMD parts...and sorry only Sprint Layout6

my working DIP version.zip

[reptooyep]

Well, I have made two versions, DIP and also SMT, both are working very well with my selfmaded DD27 coils.
Fred

Hi Fred,
Could you share your DD coil data (wire gauge, n° of turns and inductance) ? My electronic is good but i have trouble nulling the coil.
Thanks

[CDI]

[ATTACH]36852[/ATTACH]


yes for sure

Many thanks Blobber.

[blobber]

Hi Fred,
Could you share your DD coil data (wire gauge, n° of turns and inductance) ? My electronic is good but i have trouble nulling the coil.
Thanks

Well as I remember right it was 50 turns 0,5 mm for TX, 200 turns 0,25 mm for RXBut I think, this is not critical, because I also used, while experimenting with Krot, my IDX and even my Bandido/TGSL coils, all are 27DD, with not bad results.
In my opinion, the first important thing, is to get the right offset or distance between TX and RX, 1,5kHz Ftx>Frx.
For this purpose, I was using a simple oscillator circuit, assembled on a bread board, by measurement the frequency, with an oscilloscope. Maybe also will working a frequency counter programm for your computer audio card. Also multimeter with frequency range will work too.
What you have to select, are the correct values for the capacitors in TX and RX tank, by the frequency which you want to get.
Approximately calculation with a LC calculator is helpful. For example TX 8,761 kHz/ 1,5 mH, C= 220 nF and RX 7,261 kHz/ 20 mH, C=20 nF.
When you put the selected capacitors in your DIP or SMD board, or directly in your coil, you can start the coil nulling, with your Mole, but be sure that automatic coil nulling is switched off (A=0; I=0)
Reduce the current in TX circuit and by sweeping your coils, you will get the minimum voltage.
The second and in my opinion, even more important thing, is the fine tuning coil balance, with one or two pice or washers or coins of iron, aluminum, ferrite...as you can see here in this Video from Andrew.


www.youtube.com/watch?app=desktop&persist_app=1&v=aUeVzWuGJIw


I suggest also, to switch off auto balance in the menu, bevor fine tuning. I realized, that with careful fine tuning, you not need auto balance.
Fine tuning should be done in final setup your machine, with rod, handle, coil..... and of course in a metal free environment with little electrical interferences.
Good luck!!